A great question that the survival literature deals with rarely. I can't think of any specific meditation-type methods out there. I can tell you what my colleague and NOLS wilderness medicine instructor Bill Downey says to his students once they have dealt with treating an injury: "If you are seriously injured, then open a can of Toughen-Up and swig it down."
Dealing with debilitating pain is going to be a mental issue once you have physically stabilized the injury. The pain associated with a broken femur will be off the Richter scale, to say the least, so any method for coping with that kind of pain, is going to be coupled with intense cussing as well!
In his riveting book Miracle in the Andes , plane crash survivor Nando Parrado spoke of focusing on his breathing to help calm his mind. This exercise took his mind off of his severely fractured skull and the loss of his sister and mother in the crash. In the end, he survived despite horrible conditions. Deep breathing is something we all use when fear is awakened in our brain. Remember the last time you narrowly avoided someone blowing through a red light? I have used deep breathing the most when coping with my own ordeals with pain, from suffering through a filling at the dentist to coping with a backcountry mishap. Mindful breathing is at the center of yoga, tai-chi, and other forms of meditation. I would consider you start there and develop your own methods for calming the mind.
Most people struggle because they don't have a reason to fight the pain and stay alive. You immediately have to identify a reason to survive. Think about the most important thing in your life and why it's worth living through adversity for it. Your will is going to be tested when the sun is setting and you are stranded in the wild.
So, my advice, short of taking those painkillers you stowed in the first-aid kit ahead of time, is to concentrate on breathing and trying to relax. After that, it's all about your desire to make it back home to the ones you love.